Problem: Which of these numbers is composite? ${4,\ 7,\ 23,\ 29,\ 41}$
Explanation: A composite number is a number that has more than two factors (including 1 and itself). 7, 23, 29, and 41 each have only two factors. The factors of 4 are 1, 2, and 4. Thus, 4 is the composite number.